Gear pump with deflector in fluid intake for diverting fluid towards voids in housing

ABSTRACT

In accordance with one embodiment, the gear pump comprises a first gear meshed with a second gear as well as a housing, in which the gears are supported. The housing includes a first void, which at least partly adjoins a first side surface of the first gear, and a second void, which at least partly adjoins a second side surface of the first gear. The gear pump further comprises a fluid intake channel configured to direct fluid towards the gears, wherein at least one deflector is arranged within the fluid intake such that an incident fluid flow is diverted towards the first void as well as to the second void.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/430,251, entitled “Gear Pump with Deflector in Fluid Intake forDiverting Fluid Towards Voids in Housing,” filed Feb. 10, 2017. U.S.patent application Ser. No. 15/430,251 claims priority to German PatentApplication No. 10 2016 102 433.3, entitled “Gear Pump,” filed Feb. 11,2016. The entire contents of the above-cited applications are herebyincorporated by reference in their entirety for all purposes.

TECHNICAL FIELD

The present disclosure relates to the field of pump design, inparticular to a gear pump, which may be employed as an oil pump in aninternal combustion engine.

BACKGROUND

A gear pump uses the meshing of gear wheels (gears) to pump fluidthrough fluid displacement. Gear pumps are one of the most common typesof pumps for hydraulic applications. For example, oil pumps used ininternal combustion engines are usually implemented as gear pumps. Gearpumps are also widely used in chemical installations to pump highlyviscous fluids. Basically, two different types of gear pumps exist, i.e.external gear pumps, which use two external spur gears, and internalgear pumps, which use an external spur gear and an internal spur gear.

As the gears rotate, the gear teeth come out of mesh on the intake side(suction side) of the pump thereby creating a void and respectivesuction. The void is filled by fluid, which is carried by the gears tothe outlet side (pressure side) of the pump, where the meshing of thegears displaces the fluid. The mechanical clearances are small (on theorder of a few 10 micrometers), and the tight clearances, along with thespeed of rotation, effectively prevent the fluid from leaking back.Usually, the rigid design of the gears and the housing allows for veryhigh pressures and the ability to pump highly viscous fluids.

External gear pumps are usually designed such that, on the intake side,the fluid (e.g. oil) flows towards the gears in a radial direction(radial inflow). In this regard the terms “radial” and “axial” refer tothe rotation of the gears. Particularly when two engaged teeth of twomeshed gears are about to come out of the mesh at the intake side of thepump, the above-mentioned void does not yet have a radial connection tothe intake channel and path of the fluid is still blocked by the teethof the gears. At the same time the volume between the two meshed teeth(not yet filled with fluid) becomes larger, which leads to a drop ofpressure in this volume. When the two teeth finally disengage, theradial connection between the above-mentioned void and the intakesuddenly opens, which may lead to an abrupt increase of local pressureand, in the worst case, to cavitation. The resulting pressure variationsmay impede the fluid flow into the void, deteriorate the volumetricefficiency of the pump, and increase undesired leakage. In particular,the sudden pressure drops of the opening teeth may suck oil through thesmall sealing gap (clearance seal) from the pressure side of the pump,which gives rise to additional leakage.

In view of the above explanation, one object of the present disclosuremay be to provide a gear pump with improved efficiency. This object isachieved by the gear pump of claim 1. Various embodiments and furtherdevelopments are covered by the dependent claims.

SUMMARY

A gear pump is described herein. In accordance with one embodiment, thegear pump comprises a first gear meshed with a second gear as well as ahousing in which the gears are supported. The housing includes a firstvoid, which at least partly adjoins a first side surface of the firstgear, and a second void, which at least partly adjoins a second sidesurface of the first gear. The gear pump further comprises a fluidintake channel configured to direct fluid towards the gears, wherein atleast one deflector is arranged within the fluid intake such that anincident fluid flow is diverted towards the first void as well as to thesecond void.

In one embodiment the deflector is shaped and positioned such that theincident fluid flow is split into a first portion and a at least asecond portion, wherein the first portion of the fluid flow is divertedtowards the first void and the second portion of the fluid flow isdiverted towards the second void. The deflector may be shaped such thatthe incident fluid flow is prevented from directly flowing towardscircumferential surfaces of the gears in a radial direction. Thedeflector may be either an integral component of the housing or aseparate component that is mounted to an inner surface of the intakechannel or the housing. A further deflector may be arranged such so asto guide the first portion of the fluid flow towards the first void.

The first void may be formed by a recess that is formed in an innersurface of a cover of the housing. The second void may be formed by arecess that is formed in an inner surface of the housing. Additionallyor alternatively, the second void may be formed by an indentation thatis formed within the intake adjacent to the second side surface of thefirst gear. In various embodiments, the first and the second voids areaxially neighboring the gears on opposing sides of the gears.

In some embodiments the duct forming the fluid intake is slanted (notin-line) with respect to a duct forming the fluid outlet. The intakechannel may be arranged at least partly in the interior of the housing.Additionally or alternatively, the intake channel may be at least partlyformed by a duct externally attached to the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure can be better understood with reference to thefollowing description and drawings. The components in the figures arenot necessarily to scale, emphasis instead being placed uponillustrating the principles of the present disclosure. Moreover, in thefigures, like reference numerals designate corresponding parts. In thedrawings:

FIG. 1 illustrates an isometric sectional view of an exemplary gearpump.

FIG. 2 illustrates another section view of the gear pump of FIG. 1.

FIG. 3 schematically illustrates a first embodiment of a gear pump, theillustration shows the intake side of a gear pump, wherein the fluidpasses the intake substantially in a radial direction.

FIG. 4 schematically illustrates a second embodiment of a gear pump, theillustration shows the intake side of a gear pump, wherein the fluidpasses the intake substantially in an axial direction.

FIG. 5A illustrates an isometric sectional view of a third embodiment ofa gear pump.

FIG. 5B illustrates a further sectional view of a third embodiment of agear pump.

FIG. 6 illustrates the cover of the pump housing of the embodiments ofFIGS. 5A and 5B.

DETAILED DESCRIPTION

The following description relates to an oil pump as an illustrativeexample of a gear pump. Such oil pumps may be used, for example, as partof the lubrication system of an internal combustion system. It isunderstood, however, that gear pumps implemented in accordance with theembodiments described herein may be readily used in non-automotiveapplications and also used to pump fluids other than oil.

FIG. 1 illustrates one exemplary gear pump 1, which may be employed topump oil, for example, from an oil reservoir to the cylinder heads of aninternal combustion engines. FIG. 1 illustrates the housing 10 of thegear pump, which includes the housing cover 11. FIG. 1 is a sectionalview through the intake portion of the pump so that the interior of theintake channel 12 is visible as well as one of the two gear wheels(first gear 20) that are supported within housing 10. In the ductforming the intake channel 12 of the pump a baffle 30 is provided whichdirects the inflowing oil towards the gears. The arrow schematicallyindicates the direction of the inflowing oil. Due to the baffle, the oilreaches the gears partly (in a substantial axial direction) at the lowerside surfaces of the gears and partly (in a substantial radialdirection) at the circumferential side of the gears.

FIG. 2 illustrates another sectional view of the exemplary pump shown inFIG. 1. In FIG. 2, the cover 11 has been removed to allow a top viewinto the housing 10 of the gear pump 1. FIG. 2 shows the two meshedgears (first gear 20 and second gear 21) as well as a portion of theduct forming the outlet 13 on the pressure side of the pump. Asmentioned above, when two engaged teeth of the gears 20, 21 disengage, asudden pressure drop may occur giving rise to increased leakage andreduced efficiency. Furthermore, the baffle 30 (see also FIG. 1) createsa kind of “bottleneck” that throttles the cross sectional area availablefor the oil to pass through towards the gears. In addition to this, theoil flow next to the gears (i.e. in the void 15 under the lower sidesurface of gear 20) may give rise to turbulences caused by thecountermotion of the oil stream as compared to the gear motion.

To improve the situation, the duct forming the oil intake channel 12 maybe designed such that the inflowing oil is diverted into voids, whichare located axially right and left of at least one of the gears 20, 21.The mentioned diverting is accomplished by a deflector or a system ofdeflectors arranged within the intake channel 12 of the gear pump. Thevoids may be formed by recesses in the cover 11 and the housing 10. Atleast one of the voids may be formed by an indentation in the intakechannel 12 adjacent to a side surface of the gear 20. The deflectordiverts the incident oil flow towards the mentioned voids thereby,firstly, generating a dynamic pressure within the voids and, secondly,preventing the incident oil flow from directly reaching thecircumferential surface of the gears 20, 21 from a radial direction.

FIG. 3 illustrates one simple exemplary embodiment implementing theconcept explained above. FIG. 3 is a cross-sectional view illustrating agear 20 of a gear pump supported in a housing 10 with a removablehousing cover 11. The duct forming the oil intake channel 12 extendsessentially in a radial direction (perpendicular to the rotation axis ofthe gears). A first recess 15 a is provided in the cover 11 and a secondrecess 15 b is provided in the housing 10. Both recesses form voidswhich are located (when looking in a radial direction) left and right ofthe gear 20 and at least partially adjoining the lower (left) and theupper (right) side surface 16 a, 16 b of the gear 20. A deflector 31 isarranged within the intake channel 12. As mentioned, the deflector 31 isdesigned such that it diverts the (radially) incident oil flow towardsthe voids formed by the recesses 15 a and 15 b thereby creating adynamic pressure in the voids on both sides of the gears (i.e. axiallyabove and axially below the gears).

FIG. 4 illustrates another simple embodiment implementing the conceptexplained above. FIG. 4 is a cross-sectional view illustrating a gear 20of a gear pump supported in a housing 10 with a removable housing cover11. As opposed to the previous example of FIG. 3, the duct forming theoil intake channel 12 extends essentially in an axial direction(parallel to the rotation axis of the gears). Similar to the previousexample, a first recess 15 a is provided in the cover 11 and a secondrecess 15 b is provided in the housing 10, wherein both recesses formvoids which at least partly adjoin the side surfaces 16 a, 16 b of thegear 20 (and the second gear 21 not shown in FIG. 4). The second recess15 b may also be regarded as an indentation in the intake channel 12adjacent to the side surface 16 b of the gear 20. A deflector 31 isarranged within the intake channel 12 and, in the present example, thedeflector 31 is designed such that it diverts the (axially) incident oilflow towards the voids formed by the recesses 15 a and 15 b. The effectof the deflector is practically the same as in the previous example ofFIG. 3. In both cases, the incident oil flow is “split” into twoportions, one of which being diverted to the first recess 15 a whereasthe other one is diverted to the second recess 15 b.

FIG. 5 illustrates another exemplary gear pump implementing the conceptdescribed herein. FIGS. 5A and 5B are different sectional views (withregard to different sectional planes) of the same embodiment. In bothviews the sectional plane runs through the intake channel 12 of the pumpin order to visualize the interior of the intake channel 12.Accordingly, FIG. 5 shows the gear 20 supported in the housing 10 thatincludes cover 11. The drive gear 22 is arranged outside the housing 10and mechanically coupled to the gear 20. Similar to the previousexamples a recess 15 a is provided in the inner surface of the cover 11to form a void that at least partially adjoins the upper side surface ofthe gear 20 (i.e. the void is axially above the gear 20). An indentation15 b′ forms a further void in the intake channel 12 in the interior ofthe housing 10. The further void adjoins the lower surface of the gear20 (i.e. the void is axially below the gear 20). Similar to the previousexamples, at least one deflector 31 is arranged in the intake channel12. In the present example a first deflector 31, which is arranged inthe lower part of the intake channel 12, is designed to split theincident oil flow into two portions, wherein a first (lower) portion ofthe incident oil flow is diverted to the void 15 b′ along the lowersurface of the deflector 31 and wherein the second (upper) portion ofthe incident oil flow is diverted to the recess 15 a along an uppersurface of the deflector 31. According to the present example, a furtherdeflector 32 is arranged on the inner surface of the cover 11. Thedeflector 32 is shaped such the upper portion of the incident oil flowis efficiently guided to the recess 15 a above the gears 20, 21 withoutcausing too much turbulence.

In the examples describes herein, the first deflector 31 is arranged inthe fluid intake channel 12 of the gear pump, wherein the fluid intakechannel 12 is in the interior of the housing 10. That is, the ductforming the fluid intake channel 12 on the suction side of the pump ismainly formed by the specific shaping of the interior of the housing 10.However, it is understood that, in general, at least a part of the fluidintake may be formed by a separate component, which is external to thehousing 10 and attached to the housing 10 during assembly of the gearpump.

In all embodiments, the deflector 31 may be an integral portion of thehousing 10. The housing may be made of, for example cast iron or castaluminum. That is, deflector 31 and the main part of the housing 10 maybe one piece. The recesses 15 b or the indentation 15 b′ forming thevoid in the intake channel 12 may either be made by using anappropriately shaped casting mold or using a subsequent abrasivemachining process, for example by milling the recess into the casthousing 10. Alternatively, the deflector 31 may be a separate componentwhich is mounted in the intake channel 12 of the gear pump duringassembly. Thereby the deflector 31 may be screwed, welded or glued to aninner surface of the intake channel 12. Generally, the deflector 31itself may be one piece or composed of two or more pieces which arejoined to form the deflector 31. In any embodiment the deflector mayhave any geometric shape and mounted in any position, provided that theshape and the position of the deflector 31 are such that the incidentfluid flow is split into a first portion and a at least a secondportion, wherein the first portion of the fluid flow is diverted towardsthe first void (recess 15 a) and the second portion of the fluid flow isdiverted towards the second void (recess 15 b or indentation 15 b′, seeFIGS. 3 to 6).

FIG. 6 illustrates one example of the cover 11. As can be seen in FIG.6, the inner surface of the cover 11 may include sleeves, which formparts of plain bearings 25, 26 of the gears 20, 21, respectively. Theinner surface of the cover 11 further includes the recess 15 a formingthe void axially above the gears 20, 21 (see FIG. 5B). Furthermore, FIG.6 illustrates the second deflector 32 arranged on the inner surface ofthe cover 11. In the present example, the deflector 32 is an integralpart of the cover 11, wherein cover 11 and deflector 32 are produced inone piece. For example the cover 11 as well as the body of the housing10 may be made of cast iron or cast aluminum. The recess 15 a may,however, also be produced by a subsequent abrasive machining process,for example by milling the recess into the cast cover 11.

Although the present disclosure has been illustrated and described withrespect to one or more implementations, variations and/or modificationsmay be made to the illustrated examples without departing from thespirit and scope of the appended claims. In particular regard to thevarious functions performed by the above described components orstructures (units, assemblies, devices, circuits, systems, etc.), theterms (including a reference to a “means”) used to describe suchcomponents are intended to correspond—unless otherwise indicated—to anycomponent or structure which performs the specified function of thedescribed component (e.g., that is functionally equivalent), even thoughnot structurally equivalent to the disclosed structure, which performsthe function in the herein illustrated exemplary implementations of thepresent disclosure.

In addition, while a particular feature of the present disclosure mayhave been disclosed with respect to only one of several implementations,such feature may be combined with one or more other features of theother implementations as may be desired and advantageous for any givenor particular application. Furthermore, to the extent that the terms“including”, “includes”, “having”, “has”, “with”, or variants thereofare used in either the detailed description and the claims, such termsare intended to be inclusive in a manner similar to the term“comprising”.

1. An external gear pump comprising: a first external gear meshed with asecond external gear; a housing, in which the gears are supported,wherein the housing includes a first void, which at least partly adjoinsa first side surface of the first external gear, and a second void,which at least partly adjoins a second side surface of the firstexternal gear; a fluid intake channel configured to direct fluid towardsthe gears; and at least one deflector arranged within the fluid intakechannel such that an incident fluid flow is diverted towards the firstvoid as well as to the second void.
 2. The external gear pump accordingto claim 1, wherein the deflector is shaped and positioned such that theincident fluid flow is split into a first portion and at least a secondportion, wherein the first portion of the fluid flow is diverted towardsthe first void and the second portion of the fluid flow is divertedtowards the second void.
 3. The external gear pump according to claim 2,further comprising a further deflector arranged such so as to guide thefirst portion of the fluid flow towards the first void.
 4. The externalgear pump according to claim 1, wherein the first void is formed by arecess formed in an inner surface of a cover of the housing.
 5. Theexternal gear pump according to claim 1, wherein the second void isformed by a recess formed in an inner surface of the housing.
 6. Theexternal gear pump according to claim 1, wherein the second void isformed by an indentation formed within the fluid intake channel adjacentto the second side surface of the first external gear.
 7. The externalgear pump according to claim 1, wherein the first and the second voidsare axially neighboring the gears on opposing sides of the gears.
 8. Theexternal gear pump according to claim 1, wherein the deflector is shapedsuch that the incident fluid flow is prevented from directly flowingtowards circumferential surfaces of the gears in a radial direction. 9.The external gear pump according to claim 1, further comprising a fluidoutlet, wherein a duct forming the fluid intake channel is slanted withrespect to a duct forming the fluid outlet.
 10. The external gear pumpaccording to claim 1, wherein the deflector is an integral component ofthe housing.
 11. The external gear pump according to claim 1, whereinthe deflector is a separate component mounted to an inner surface of thefluid intake channel or the housing.
 12. The external gear pumpaccording to claim 1, wherein the fluid intake channel is arranged atleast partly in an interior of the housing and/or wherein the fluidintake channel is at least partly formed by a duct externally attachedto the housing.